Heretofore, fast attachment of plastic lamp housings of the class mentioned above to body panels of automobiles has been generally accomplished by use of bolts and nuts. Exposure to view of the heads of such bolts used in the plastic lamp housings is detestable because these plastic lamp housings serve as ornamental parts in the overall appearance of automobiles in addition to fulfilling their basic function of protecting the lamps encased therewith. To prevent the bolts from such exposure, the bolts are inserted in position within the plastic housings when the housings are injection molded with plastics.
A typical conventional structure in which bolts are inserted in plastic housings as described above is illustrated in FIG. 1. This structure will be described below with reference to FIG. 1. First, the common structure of a housing 1 itself will be described. A lamp case 2 in the shape of a box serves to encase a lamp (not shown). A space 3 for receiving the lamp in the lamp case is provided on the edge surrounding the opening thereof with flanges 4. These flanges 4 are destined to come into contact with the front surface of a body panel 5 of an automobile, while the lamp case 2 is inserted through an insertion hole 6 perforated in the body panel 5 and set in position inside the shell of the automobile.
To the front sides of the flanges is attached a cover 7 permeable to light. The cover serves to protect the lamp held inside and, at the same time, permit passage of light issuing from the lamp within the lamp case. The relation of the union between the lamp case 2 and the cover 7 has no bearing whatever upon the present invention, because this invention as will become apparent from further disclosure of the invention made hereinbelow, is applicable to any lamp housing 1 on the condition that the housing is provided with such flanges 4 as mentioned above and also with a lamp case 2.
For attachment of the housing 1 of this type to the body panel 5, convention has prescribed that weld bolts 8 be insert molded in the flanges 4 of the housing 1 at the time that the housing 1 is injection molded with plastics, these weld bolts 8 be inserted through perforations 9 (refer also to the diagram of FIG. 2 illustrating the front side of the body panel) and thrust out of the rear side of the panel at the same time that the lamp case 2 is sunken through the insertion hole 6, washers 10 be slid over the projected bolts from behind the rear side of the panel, and nuts 11 be threaded upon the bolts. Generally, a seal packing 12 is nipped between the flanges 4 of the housing 1 and the panel 5.
The fixing structure of this principle, however, suffers from numerous drawbacks such as, for example:
(1) The insert molding of bolts 8 is a troublesome work which takes up much time and calls for much cost. PA0 (2) When tie insert molding of bolts is effected in a large lamp housing, the strain of resin which ensues during the curing of the housing poses itself a serious problem. The strain is so serious as to render it difficult for the bolts to be retained in a straight upright position. With the insert molding, therefore, it is difficult to ensure high dimensional accuracy in the fixing of the housing on the automobile body. PA0 (3) The fixing structure entails the so-called two-face work across the panel, that is, one work for inserting the housing on the front side of the panel 5 and the other work for rotatably driving nuts 11 round the bolts on the rear side of the panel 5. This is highly inefficient, time-consuming work which requires use of tools. PA0 (4) As regards the work for boring holes in the body panel 5, the fixing structure under discussion necessitates formation of perforations 9 to be used exclusively for insertion of bolts around the edge of the insertion hole 5 formed for the insertion of the lamp case 2 as illustrated in FIG. 2. The boring work itself is troublesome and the work of positioning the perforations accurately relative to the insertion hole and relative to one another is not easy. PA0 (5) The seal packing 12 is naturally required to be perforated to permit passage of the bolts 8. The relevant portions of the sealing area are consequently sacrificed. PA0 (6) When housings of similar sizes are fixed at different positions, the positions of bolts inserted in the housings are different. After all, different metal dies are required for the injection molding of such housings despite their similar sizes. This calls for both time and cost.
As an improvement over such a conventional fixing structure, there has been proposed a fixing structure having anchor-shaped plastic fasteners integrally molded with a housing in place of such bolts (Japanese Utility Model Disclosure No. SHO 52(1977)-135772). With this particular fixing structure, the last three (4), (5), and (6) of the aforementioned drawbacks still persist, although the first three drawbacks (1), (2), and (3) are no longer suffered.
Apart from the disadvantage, the work of molding fasteners, which are extremely small as compared with the housing and which require high dimensional accuracy, in conjunction with the housing in one and the same mold is irrational in the first place. Some fasteners have complicated shapes such that they cannot be released from a mold unless the mold is separable along a plurality of planes. Such a mold is too expensive to render the device itself feasible.